In most integrated circuit applications, there is a need for structures which function as resistors. For years, lightly-doped polysilicon strips have been used as resistors in a wide variety of applications. U.S. Pat. No. 4,209,716, issued to Joseph H. Raymond of Texas Instruments is an example of the use of lightly-doped polysilicon resistor technology in an SRAM application. Most SRAM manufacturers have abandoned this particular use of polysilicon resistors for several reasons. Not only is the resistivity of polysilicon non-linear with respect to voltage, but it is difficult to achieve resistive value consistency in such structures due to a three variables: deposition-related polysilicon film thickness, etch-dependant film width, and doping levels. The three variables interact to establish the resistive value of the structure. Because the variability is too great for megabit SRAMs, most manufactures utilize back-to-back diodes constructed on a polysilicon strip to create resistive structures.
There is a growing need for highly-reliable and highly-stable resistors having resistivities in the giga-ohm range. SRAMs are but one potential application. Field emission displays are another. In field emission displays having cold cathode emitters, stable and reliable resistors having uniform resistivity throughout the display are required to prevent runaway current from the cathode to either the anode plate and/or grid electrodes. Runaway cathode current severely degrades the lifetime of the emitter tips and also raises power consumption to levels which, for most intended applications, are unacceptable.